In recent years, CMOS image sensors have been actively developed. Particularly, as miniaturization (according to a design rule for miniaturization) is progressing in semiconductor processes, single-panel color image sensors with more than 10 million pixels at pixel pitch of 1.4 μm, for example, are already available on the market. In the trend of the increasing numbers of pixels, attempts are being made to obtain physical information that has not been obtained due to the use of a large number of pixels, such as a distance to an object.
There has been a known imaging element that obtains information about the distance from the imaging element to an object by inserting a microlens array as a compound-eye optical system between the imaging lens and the imaging sensor. However, with this imaging element, the S/N ratio and the resolution of an image cannot be restored satisfactorily when the single image is re-formed by combining images formed by respective microlenses.